Villasillo2008's Weblog

IC and the Potassium Chloride Sensitivity Test

Many IC patients have expressed their concerns regarding the usefulness of the potassium chloride sensitivity test (also known as the KCl Sensitivity Test or Parsons Test), in diagnosing and treating IC. The ICA has also received comments from patients regarding the pain induced by the test. More and more patients report that their physicians are relying on this test to diagnose IC, and to predict their response to medications. However, careful investigation and consideration of all available information regarding the KCl Test must be taken into account before accepting the validity of the test. This test has yet to be proven or accepted as a diagnostic or predictive IC test.
 
What is the KCL Test and What is it Used For?
The test consists of instilling a solution of potassium chloride, known chemically as KCl, into the bladder via urinary catheter. It has been suggested for two uses: 1) a diagnostic test for IC; 2) a predictive test for response to IC-specific medications such as Elmiron® and other heparinoids that are thought to work by coating the bladder lining.
 
Is the KCL Test an Accurate Diagnostic Test? 
The KCl Sensitivity Test was originally designed as a possible diagnostic test for IC.1 Yet, based on current available data, this test lacks accuracy. One study found the KCl sensitivity test to be 75 percent accurate, i.e. if 100 IC patients are given this test, only 75 of these patients will be diagnosed accurately. Another study found the test to be only 60 percent accurate in the diagnosis of IC. 2 More recently published data suggest that the KCl Sensitivity Test should not be considered as a reliable tool for the diagnosis of IC.3 These researchers propose that clinical findings (urinary urgency, frequency, and/or pain in the absence of other urological conditions), along with cystoscopy/hydrodistention under general or regional anesthesia, are still the most consistently accurate and reliable means of diagnosing IC. 4
 
Is the KCL Test an Accurate Predictive Test?
The KCl Sensitivity Test is currently being evaluated as a predictive test. The test is thought to be able to gauge the permeability of the glycosaminoglycans (GAG) layer of the bladder, which may be defective in some IC patients. Some investigators believe that IC patients who respond positively to the test will be more likely to be helped by a specific class of IC treatments—the mucosal surface protectants or “heparinoids”—such as oral Elmiron®, intravesical heparin, etc. 5,6 However, its usefulness as a predictor of response to heparinoids has not been substantiated. 7
 
Is the Test Painful?
During the test, patients are asked to report the degree of severity of pain/urgency that they experience while the KCl solution is in the bladder. This pain response may be present not only during, but after the test, and can last as long as days to weeks following the procedure. And, it may be difficult for patients to accurately quantify an increase in pain when they may already be in considerable pain prior to administration of the test. It has been suggested that Marcaine® (long-acting anesthetic, similar to lidocaine) and heparin be instilled into the bladder immediately after the KCl Sensitivity Test, so that the potential for a painful flare-up is reduced. Some patients have required opioid analgesics to ease the pain after this procedure.
 
Can the Test be Misinterpreted?
Of primary concern is that if the test results are negative, urologists may mistakenly tell their patients that they do not have IC. Also, because of the test’s considerable publicity, it is possible that the KCl Sensitivity Test could be accepted by many urologists and other physicians as a reliable substitution for the standard IC diagnostic test—cystoscopy with hydrodistention under general or regional anesthesia, which is still considered the “gold standard” for diagnosis of IC.

The KCl Sensitivity Test is also not specific for IC. Patients with acute urinary tract infection, radiation cystitis, other inflammatory conditions of the bladder, and those receiving chemotherapy for bladder cancer may also have a positive response to the test. Furthermore, the test may be negative, even if a patient has IC, if the patient: 1) has recently received DMSO or heparin intravesical instillations; 2) has recently undergone hydrodistention; 3) has been taking Elmiron® ; and/or 4) does not exhibit bladder permeability as a part of their IC.

If the above conditions have been ruled out, and the patient has symptoms consistent with IC, then the patient could be treated empirically, rather than be subjected to this painful test.
 
Are any other Diagnostic Tests being Investigated?
There are less painful, less invasive, and more accurate diagnostic tests currently under investigation that will hopefully lead to a commercially available test in the future. Researchers have identified two factors that may explain changes in the bladder of IC patients. The first factor is a heparin-binding epidermal growth factor (HB-EGF), important for cell growth and healing. This factor is significantly decreased in the urine of IC patients when compared with specimens from healthy people or patients with other urologic conditions, such as urinary tract infections. The second factor is a protein known as an antiproliferative factor (APF) which has been isolated in IC patient urine specimens. This protein may prevent the growth of new, healthy bladder lining cells. These research findings could lead to a diagnostic test for IC as well as a new treatment. 8, 9, 10, 11

Also, a lactulose/rhamnose test, similar to the test used to diagnose gastrointestinal permeability, is being investigated.12 This test for bladder permeability involves instilling a sugar solution into the bladder and subsequently checking for levels of this sugar molecule in the serum. This new permeability test may distinguish intact versus permeable bladders, and is far less traumatic to the patient when compared to the potassium test.
 
Conclusion
The KCl Sensitivity Test is a painful test to administer to patients, many of whom present initially with significant pain. If your doctor feels that it is necessary to use the KCl Sensitivity Test to as a diagnostic test for IC, you should insist on the following:

1. Remind your doctor that should your results be negative, you still may have IC. The published medical literature reports approximately a 40 percent false negative rate. This means that for every 100 people with IC undergoing the test, 40 of these people will have no response to the test solution placed in their bladders. Again, this does not mean that you do not have IC. It is a limitation of the test itself.

2. After the KCl Sensitivity Test is performed, a solution of Marcaine® should be placed into your bladder, regardless of whether or not the test initially caused pain. Marcaine will help to reduce the painful symptoms that may occur minutes to hours after the test is given.

3. You should be given a prescription for pain medication (Vicodin®, for example), since this test can trigger a flare in symptoms. On occasion, the flare can be severe, and may require additional medications, such as B & O® suppositories or stronger pain medication.